Heating coil



A. T. LEWIS ET AL HEATING COIL July 4, 1933.

2 Sheets-Sheet 1 Original Filed May 9, 192a I INVENTORS I WLEX/VNQER- Z law/s,

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A TTORNE Y July 4, 1933., A; T. LEWIS EF AL I HEATING COIL Original Filed May 9, 1928 2 Sheets-Sheet 2 ,5 5 E I R Wmmmm E n? RE, mmfi mp".

' cal position; and Fig. represents asec- "Patented July 4, 1933' *UNITED STATES PATENT-HOFFICF.

ALEXANDER THORNTON 'LEW'IS AND DONALD E. FRENCH, OF MERION, PENNSYL- VANIA, ASSIGNORS, BY HESNE ASSIGNMENTS, TO CARRIER RESEARCH CORPORA- TION, OF NEWARK,

Original application and m 9, was, I I

. 1929. Serial The present invention relates to heating apparatus and more particularly to a heating coil of unitary construction, and th1s appl cation isa division of a 'co-pending applicat on Serial No. 260,458 filed May 9, 1928,'wh1ch has since matured into PatentNo. 1,7 51,865, dated March 25, 1930.

Some of the objects of the present invention are to provide an improved heating coil; to provide a heating coll consisting of tubes and headers having the ends of; the tubes integrally united thereto; to provide a pipe coil heating unit so arranged and constructed that the stress and strains caused by expansion and contraction are automatically absorbed and have no eifect upon the joint between the pipes or tubes and the headers; to provide a coil structure for indirect heatinghnits whereln a maximum heating surface and a maximumv passage for air. are obtained; and to provide 7 other improvements as will hereinafter appear. v g

In the accompanying drawmgs,F1g. 1 represents a plan of a heating co1l embod y1ng one form of the present invent1on; Fig. 2

represents a side elevation of the same; 3 represents an end elevation of.F1g. 1; Fig.

' 4-representsan enlarged detail showing the tube pitch of the unit when placed in a vertitional detail of the tube construction after the uniting operation.

' Referring to'the drawings, one formof the present invention comprises a heating c'oil consisting generally ofan inlet header 10, an

f outlet header 11, and interconnecting-heater tubes '12 through which the heating medium is circulated. Inthe present instance, the headers and 11 are steel, while the tubes 12 are of copper, though it will be understood the invention is not specifically limited I to these two metalsbut might be appliedv or embodied in other heating units having headersand tubes. It should also be noted that Fig. 3 illustratesthe heating unit of the present invention in its vertical position, in which case one header is staggered horizontally with.respect to the other so that there. is a free gravity flow of an liquidin the tubes 12 for return purposes, t ough such staggered dimensionsthere is always an unrestricte NEW JERSEY, A. CORPORATION OF NEW JERSEY firearms con. i

flerial'No. 260,458. Divided'and this application filed January 18,

relation of the headers is unnecessary where the unit is mounted in a horizontal position because the naturalpitchof the tubes allows for the desired return. I I

The headers 10 and 11, respectively, consist 1' of header plates 13 and 14' provided with through holes 15 and 16 (here shown as of the same size because the tubes are preferablyof the same diameter) for the rece tion of the respective tubes 12, and casingsl and 18 of tubular form which are respectively attached to theheader plates 13 and 14 in a'leak proof manner, such as by Welding thereto, as shown at 19. The size of thecasing 17 is such as to provide a chamber 20 which communicates with all of the inlet ends of the tubes 12, while the casing .18 is of such a size as to provide a chamber 21 communicating with all of the outlet ends of the tubes 12. At a convenient point, the casing 17 is pro-.

loop 24 and returns with substantially, the

' same downward pitch to the outer header 11. For maximum tube area with maximum air circulating space, one row of the tube inlets '15 is staggered with respect to the other row.

' of inlets 15, and one row of tube outlets 16 is staggered with respect to the other row of tube outlets, and in this instance the staggered distance in each case is substantially equal sult, all of the tube returns or loops 24 at both ends are substantially in contact with each other at opposite sides while the body lengths of the tubes are separated by spaces 25 which communicate with a space 26 formed between,

' the inlet and outlet lengths of the coils. This space 26' is variable with the arc of the loops 24, while the spaces 25 are variablein accordance with the distances between theholes in the header, but whatever the variation in vi'de'd with an inlet nipple 22, and similarly mined distance, then ma es a reverse bend or.

to the outside diameter of a tube. As a, re-. .5

I joint between the fins and the tubes.

tortuous path between the pipe coils for the passage of air in contact with the fins 28 which are mounted upon the length of each tube between the loop ends. While this construction provides an eflective heat absorbing path for the air, it also furnishes an efiective means for automatically compensating for expanion and contraction of the tubing due to changes of temperature. Thus because the two headers are located substantially'adj acent one another and are interconnected by substantially U-shaped tubes, the joints between the tubes and headers are not subjected to expansion strains andstresses because the body of each of the tubes is free to move and automatically adjust itself to a change in temperature.

In order to form-a leak proof joint between the tube ends and the headers and to provide a joint which unites the parts with an integral construction, each tube 12 has its ends inserted in the respective holes 15 and 16 of the header plates 13 and 14 with a clearance fit, while theannular marginal edges of the respective tubes preferably project slightly beyond the lane of the outer face of the header plates. lso it should be noted that the holes in header plates 13 and 14: are counter bored on the outer face of each header to form annular grooves 29 for .the'reception of the bonding material. When the tubes have been as sembled in the header plates 13 and 14 with their ends protruding through the counterbore grooves 29, each is successively subjected to the action of a welding torch simultaneously with the application of a bonding material to the joint between the tubes and plates. This bonding material is preferably an alloy, such as bronze, though it may be any other suitable bonding material which has a fusing point approximating the fusing point of copper or other material of which the tube is.

made. The uniting action, therefore, takes place at a temperature substantially that of the fusing point of copper, and as a result each tube is joined to its plate by an annular ring 27 formed as an integral part of the plate by the simultaneous fusing of the bonding material and the material of the plate. 7

Since one of. the main features of the present invention is the formation of a oint at a relatively high temperature, say for example a temperature not less than 1400 F., it is evident that the desired uniting of the tube and header cannot ordinarily take place.

without damage either to the tube, or in case of finned tubes to the fins, and to the To the end, therefore, that this uniting operation can be successfully carried out without damage to the tubes, the fins or the bonding material between the tubesand fins, the present invention embodies as a. new step in joint construction the use of a bonding material which has a fusing point as near as possible 1;? the mam-a2 fusing point'of the material of the tubes. This fusing point of this bonding material should not only bewell above the annealing point of the tube material but also well above the annealing .point of the material of the fins of a'tub'e in case a finned type of tube is to be united to a header. In addition, the fusing point of the joint bonding material should be well above the melting point of any material ordinarily used to unite fins to tubes. As a component part of the present method, a step has been devised whereby the high fusing bonding material can be successfully brought to its fusing point while maintaining adjacent parts at a relatively low temperature during the fusing operation. This step consists broadly of the application of a cooling medium to parts adjacent the joint being formed and in the preferred form this cooling medium is a bath of water maintained at a low temperature and so arranged that any tube or tubes to be connected to a header plate is or are immersed in the bath erence has been made to the jointing of copper tubes to steel headers, but broadly considered the invention is not limited to any particular metal or metals, and the tubes and headers may be of the same metal instead of different metals without departing from the invention. In other words, the present invention contemplates the successful forma-' tion of a hightemperature joint, that is one capable of standing up and resisting temperatures of at least as high as 700 F., without breakdown. In the present instance, the high temperature joint. completes a unitary heating coil formed of finned tubes byan integral joining of the tubes and headers so that the entire structure is capable not only of resisting all of the strains to which connected tubes and headers are subjected but also-temperatures up to approximately 700 F.. In the ordinary jointed construction of tubes and headers, the expansion and contraction causes the joints to open and makes necessary constant repairs in the form of reexpanding, resoldering, and rejointing, while all such troubles, repairs, and delays are eliminated by the present high temperature uniting method. Also the present construction reduces to a minimum the strains and stresses transmitted to the joints because expansion and contraction are absorbed by the freely suspended looped form of the tubes. The

foregoing structure has been made possible i by a new and novel method which consists in locating the end of a tube in a prepared hole in a header plate, subjecting the body of the tube to the action of a cooling medium, 'applying a bonding material having a fusing point as near as possible to the fusing point of the metal of the tube and higher than the annealing point of the tube or any fins carried thereby and well above the melting point of any material used to unite the fins to the tube or tubes; and subjecting the bonding material, the end of the tube, and the plate to heat having a temperaturehigher than the melting point ofthe bonding material which unites the fins to the tubes.

Having thus described our invention, we claim: .v i 1. A new article of manufacture comprising a heating coil formed of two headers each including a metal plate, a tube having its ends terminating respectively in said header plates and formed of material hav-v ing a lower fusing point than the metal of said plates, and a bonding material hav ing a fusing point approximately that of the metal of said tubes integrally uniting the tube ends and plates in fused relation.

'2; Anew article of manufacture compris-' fused relation.

3. A new article of manufacture compriseach including 'a steelplate, a plurality of copper' tubes having ends terminating respectively in said header plates, and a bonding material having a fusing point approxlmately the same as the fusing point of copper integrally uniting said tube ends and plates in fused relation 4:. A new article of manufacture comprising a heating coil formed of two headers each including a steel plate, a plurality of finned loop shaped copper tubes having ends terminating respectively in said header plates, and a bonding material having a fusing point approximately the same-as the 'fusing point of copper integrally uniting said tube ends and plates in fused relation.

5. A new article of manufacture comprising a heating coil formed of a reversely bent finned copper tube,-two header plates of material other than copper receiving respec-" tively the ends of said tube, and a bonding 'material bridging the joints between said tube ends and plates and integrally connecting said tube and plates in fused relation,

said brazing material having a fusing point .closely approximating the fusing point of ing a heating coil formed of two headerscopper.

6. A heating coil embodying as a part thereof a metal plate, provided with an opening, a tube having an end located in said opening, the material of said tube having. a lower fusing point than the metal of said plate, and a bonding material having a fusing point approximately that of the metal and plate in fused relation.

Signed at Philad lphia, county of said tube integrally uniting said tube end of Philadelphia, State of Pennsylvania, this 8th day of January, 1929. e

ALEXANDER THORNTON LEWIS. DONALD E. FRENCH. 

